Existing TRUs are configured to work with containers, trailers, and other similar transport units to control a temperature inside the transport units. Conventionally, the TRU is generally installed on one side of the transport unit where conditioned air is blown into an internal space of the transport unit. The TRU generally includes a compressor, a condenser coil, an expansion device and an evaporator coil to form a refrigeration circuit. The evaporator coil may be configured to exchange heat with indoor air of, for example, the transport unit to regulate an indoor temperature inside the transport unit.
Some TRUs can work in both cooling and heating/defrost modes. In the cooling mode, refrigerant vapor may be compressed by the compressor, then the compressed refrigerant vapor may be directed into the condenser coil to be condensed into liquid refrigerant. The liquid refrigerant may be expanded by the expansion device to become a liquid/vapor two-phase refrigerant and reduce a temperature of the refrigerant. The two-phase refrigerant may be then directed into the evaporator to exchange heat with air inside, for example, a transport unit. In a heating/defrost mode, the refrigerant vapor compressed by the compressor may be directed into the evaporator coil bypassing the condenser coil and/or the expansion device. The hot refrigerant vapor may exchange heat with the indoor air in the evaporator coil.